CVE-2025-3446 in Mattermost
Summary
by MITRE • 05/15/2025
Mattermost versions 10.6.x <= 10.6.1, 10.5.x <= 10.5.2, 10.4.x <= 10.4.4, 9.11.x <= 9.11.11 fail to check the correct permissions which allows authenticated users who only have permission to invite non-guest users to a team to add guest users to that team via the API to add a single user to a team.
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Analysis
by VulDB Data Team • 09/30/2025
This vulnerability exists in Mattermost server software where improper access control validation allows authenticated users to escalate their privileges through the API. The flaw affects multiple versions including 10.6.1, 10.5.2, 10.4.4, and 9.11.11, representing a critical permission bypass issue that undermines the platform's security model. The vulnerability stems from a failure in the permission checking mechanism within the team membership management API endpoints, specifically when processing requests to add users to teams. Users who possess only the limited permission to invite non-guest users are able to exploit this flaw to add guest users to teams despite lacking the required authorization.
The technical implementation of this vulnerability resides in the server-side validation logic where the system fails to properly verify whether the requesting user has the appropriate permissions for the specific action being performed. According to CWE-285, this represents an improper authorization flaw where the application does not correctly enforce access controls. The vulnerability allows an authenticated user to make API calls that should be restricted to administrators or users with elevated privileges, effectively bypassing the intended permission boundaries. This misconfiguration creates a path for privilege escalation through the API layer where the system fails to validate that the operation being requested aligns with the user's actual authorization level.
The operational impact of this vulnerability is significant as it enables malicious or compromised users to gain unauthorized access to guest user capabilities within team environments. This could lead to unauthorized data access, information disclosure, and potential privilege escalation within the Mattermost platform. Attackers could leverage this vulnerability to add guest users to teams they do not normally have access to, potentially allowing them to observe or interact with sensitive team communications. The flaw affects the core team management functionality and undermines the platform's ability to enforce proper user access controls. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques and potentially to initial access through compromised user credentials.
Organizations using affected Mattermost versions should immediately apply the vendor-provided security patches to remediate this vulnerability. The recommended mitigation strategy involves upgrading to the latest stable versions where proper access control validation has been implemented. Additionally, administrators should review and audit existing team membership permissions to ensure that only authorized users have the ability to invite guest users. Network monitoring should be implemented to detect unusual API activity patterns that might indicate exploitation attempts. The vulnerability highlights the importance of proper input validation and authorization checks in API implementations, particularly when dealing with user management functions that involve privilege levels and access control boundaries.